Sludge centrifuge



United States Patent [72] Inventor Walter Hoffmann Lidingo, Sweden [21]Appl. No. 803,319, [22] Filed Feb. 28, 1969 [45 I Patented Dec. 29, 1970[73] Assignee Alfa-Laval AB Tumba, Sweden a corporation of Sweden [32]Priority Feb. 29, 1968 [3 3] Sweden [31 No. 2599/68 [54] SLUDGECENTRIFUGE 8 Claims, 2 Drawing Figs.

[52] U.S. Cl 233/20 [51] Int. Cl B04b 11/02 [50] Field ofSearch 233/19,

19a, 20, 20a, 46, 47, I6

[56] References Cited UNITED STATES PATENTS 3. 1 67,509 l/l965Steinacker 233/20 3,189,267 6/1965 Thylefors 233/20 3,237,854 3/1966Thylefors 233/20 3,403,849 10/1968 Thylefors 233/20 PrimaryExaminerRobert W. Jenkins Attorney-Davis, Hoxie, Faithful and HapgoodABSTRACT: The centrifugal rotor is provided with a first valve movablehydraulically to open and close the peripheral outlet through whichcentrifugally separated sludge is discharged from the rotor, the rotorhaving another outlet for the operating liquid by which the valve isactuated. A second valve is hydraulically actuated to open thisoperating liquid outlet and is urged by a biasing means in the directionfor closing the latter outlet, the rotor also having a chamber solocated and dimensioned that a liquid substantially filling this chamberacts to urge the second valve in its closing direction with a force inaddition to the force of said biasing means.

PATENTED D582 9 I975 INVENTOR.

WALTER HOFFM BY v ANN swoon CENTRIFUGE THE DISCLOSURE This inventionrelates to sludge centrifuges of the type in which separated sludge isdischarged from the centrifugal rotor intermittently under control of afirst valve actuated hydraulically by an operating liquid for which therotor has a separate outlet adapted to be opened by hydraulic actuationof a second valve, the rotor having biasing means for urging the secondvalve in the direction for closing the operating liquid outlet.

A centrifuge of this type is disclosed in Swedish Pat. No. 125,439. Theclosing of the second valve of this centrifuge is effected by means ofbiasing springs after the main portion of the operating liquid hasdischarged through the outlet. During the later part of this dischargeperiod there is a stage of balance between the opposing forces acting toopen and to close the secondvalve, and this stage is passed relativelyslowly. Thus, the closing of the second valve will take place with anundesired delay.

According to the present invention, a more rapid closing of the secondvalve is effected by subjecting it to a hydraulic actuation in theclosing direction. More particularly, at the moment when the closing isto be effected, a liquid is supplied to a chamber so located in therotor andhaving such a radial extension that liquid substantiallyfilling the chamber is operable to give the second valve an additionalactuation in the closing direction.

Between the sludge discharges the liquid in the chamber is to be drawnoff. Even if this can take place by leakage, it is desirable to providethe chamber with a throttled outlet,-

preferably from its radially outer part.

According to a preferred embodiment of the invention, the chamber islocated in the discharge path of the operating liquid which actuates thefirst valve. Due to the fact that the chamber is filled with liquid inthis way, a closing hydraulic actuation of the second valve is obtainedvery rapidly and at a correct point of time.

According to the invention, it is possible to obtain either a total or apartial discharge of the content of the rotors separating chamber. Thetotal discharge is desired when sludge deposits caked together are tobe, removed from the sludge space, and the partial discharge is desiredwhen only deposited sludge and not separating liquid is to bedischarged. The partial discharge allows uninterrrupted supply ofseparating liquid to the centrifuge, without liquid losses occurring.

The total discharge can be obtained by giving the chamber such a volumethat it can receive all operating liquid flowing from the outlet of thefirst valve, without the second valve being actuated in its closingdirection. The closing of the second valve is obtained automaticallywhen the liquid acting to open this valve is drained from the spacewhere it effects the opening force, but such closing of the second valvecan be accelerated by supplying additionaloperating liquid to thechamber through a separate channel at the correct moment.

A desired partial discharge can be obtained by supplying a limitedquantity or a limited flow of operating liquid, corresponding to thispartial discharge, to the chamber through the separate channel. In thisway, a controlled prefilling of the chamber is effected whereby theoutlet from the first valve is closed before the total content of theseparating space has been discharged.

According to a feature of the present invention which facilitatesattaining a desired degree of partial discharge, the chamber has astarting or minimum liquid level provided by an overflow outlet withlimited outlet area and which is located, calculated radially, insidethe outer part of the chamber; and the additional operating liquid,corresponding to the desired degree of partial discharge, is supplied toand builds up from this starting level. In order to make it possible toadapt this overflow outlet to different operational situations, it ismade adjustable in the radial direction, preferably in such a way thatit can be screwed radially inward or outward by actuation from theoutside of the centrifuge rotor.

If the centrifuge is used only for partial discharge, rings of solidmaterial (metal or the like) can be placed in the chamber the volume ofthese rings corresponding to the prefilling volume which, as notedabove, is determined by the position of the overflow outlet.

The invention is described more in detail below, reference being bad tothe accompanying drawing in which FIG. 1 is an axial sectional view ofthe main part of the lefthand half of an embodiment of the newcentrifuge, and FIG. 2 is a similar view showing a fragment of amodified embodiment. In the two figures, corresponding details havethesame reference numerals.

In FIG. 1, a rotor body l is provided with a cover 2 secured by alocking ring 3. A set of conical discs 5 is provided in the separatingspace 4, and the liquid to be separated is supplied from above through adistributor 6. The centrifuge is mounted on and driven by a spindle 7.The rotor wall has sludge outlet openings 8 which are closed by a pistonvalve 9 when it is actuated upwardly by means of operating liquidsupplied through a stationary pipe 10 to a space 11 at the underside ofthe valve 9. A ring valve 13 is pressed upward by springs spaced aroundthe rotor axis and of which one is shown at 12. In the upper position ofvalve 13, its cushions 14 (made of nylon, for example) keep outlets 15from the space 11 closed. A space 16 above the valve 13 is drainedthrough throttled outlets 17. An annular chamber 18 with throttledoutlets 19 is provided in the rotor wall at the underside of the valve13. An annular chamber 20 with three different overflow outlets 21, 22and 23 is provided in the central portion of the rotor bottom. Anadditional stationary pipe 24 for the supply of operating liquid opensinto the chamber 20, and from the chamber 20 a channel 25 leads to thespace above the valve 13 and a channel 26 leads to the chamber 18. Aslot between the ring valve 13 and an annular ridge 18b on the rotorbottom is designated by 18a. The space 16 communicates with the chamber18 through channels 27 which pass through the ring valve 13 and theopenings of which at the upper sideof the ring valve are located betweenthe cushions l4.

In FIG. 2, the chamber 18 is provided with an overflow outlet 28 in theform of a pipe piece, which can be screwed radially inward or outward.

In the operation of the FIG. 1 centrifuge, after a sludge dischargethrough the openings 8, the ring valve 13 is pressed to closing positionby the springs 12, the cushions 14 closing the outlets 15. Liquid issupplied in such a quantity through the pipe 10 that the space 11 isfilled, the valve 9 being closed. Separating liquid again fills theseparating space 4. When sludge is to be discharged, an additionalquantity of liquid is supplied through thepipe 10, so that it flows overthe overflow outlet 21 and reaches the space 16 via the channel 25. Inthis space the liquid exerts such a pressure against the upper side ofthe ring valve 13 that the valve is pressed downward against the actionof the springs 12. The liquid contained in the space 11 flows (togetherwith the smaller quantity of liquid supplied through the channel 25)downward into the chamber 18 via the channels 27. The latter chamber hassuch a large volume that it can receive the whole quantity of liquidpassed into the chamber, without the liquid level in the chamber 18being displaced so far inward that the pressure generated by the liquidcauses closing of the valve 13. The latter, however, is closed by thesprings 12 when the liquid in the space 16 has been drained through theoutlets 17. In this case, there occurs a total discharge of the contentof the separating space. On the other hand, if a partial discharge ofthe content of the separating space 4 is desired, a limited quantity ora limited flow of liquid is supplied through the pipe 24, when a sludgedischarge is to be effected. In this way, a certain liquid level in thechamber 18 is provided in advance, whereby the liquid arriving from thespace 11 will displace the liquid level sufficiently inward so that theliquid in the chamber 18 and in the narrow slot 18a will, in cooperationwith the springs 12, actuate the valve 13 so that it closes earlier thanin the preceding case. Due to the fact that the slot 18a is narrow, theliquid level moves rapidly inward in this slot. This leads to a rapidincrease of the hydraulic pressure against the underside of the valve 13and to a corresponding rapid closing of the valve. Only a partialdischarge of the content of the separating space 4 now takes place. Adesired degree of partial discharge can be attained by control of theliquid supply through the pipe 24. After the valve 13 has been closed,the space 1818a is drained through the outlets 19.

In the embodiment according to FIG. 1, the liquid supply through thepipe 24 can cause the liquid level in the chamber 18 to fluctuate. Inorder to achieve an improved accuracy, as regards the degree of partialdischarge, the arrangement according to FIG. 2 is provided in thechamber 18 with an overflow outlet 28 having a limited cross section inthe form of a pipe piece which can be screwed in the radial direction.This means that operating liquid, entering from the pipe 24, fills thechamber 18 only to a level which is determined by the position of theinner opening of the pipe piece 28. Operating liquid, entering with highvelocity from the space 11, now fills the chamber 18 from a level(determined by the overflow outlet 28), with the result that the valve13 is closed after a more exact space of time than is possible in theembodiment according to FIG. 1. The said space of time can, according tothe desired degree of partial discharge, be adjusted by screwing thepipe piece 28 inward or outward. Another possibility of attaining adesired degree of partial discharge is to change the volume of theoutflow path of the liquid upstream from the chamber 18, for example, bymeans of insertion bodies (not shown).

lclaim:

l. A sludge centrifuge comprising a rotor provided with an outlet fordischarge of centrifugally separated sludge, a first valve movablehydraulically to open and close said sludge outlet, the rotor having anoutlet for an operating liquid by which said valve is actuated, a secondvalve for opening and closing said operating liquid outlet, the secondvalve being hydraulically actuated to open the operating liquid .outlet,means for biasing the second valve in the direction for closing theoperating liquid outlet, the rotor also having a chamber so located anddimensioned that a liquid substantially filling said chamber acts tourge the second valve in said closing direction with a force in additionto the force of said biasing means, and means for substantially fillingsaid chamber with a liquid.

2. A centrifuge according to claim 1, in which said chamber is disposedin the path of liquid flowing through said operating liquid outlet.

3. A centrifuge according to claim 1, in which said chamber has athrottled outlet.

4. A centrifuge according to claim 1, in which said chamber is disposedin the path of liquid flowing through said operating liquid outlet, andis adapted to receive all of the flow through said operating liquidoutlet without said second valve being actuated in its said closingdirection.

5. A centrifuge according to claim 1, in which said means forsubstantially filling said chamber include a separate channel in therotor for supplying liquid to said chamber.

6. A centrifuge according to claim 1, in which said means forsubstantially filling said chamber include a separate channel in therotor leading to the chamber, and means for supplying liquid to saidseparate channel.

7. A centrifuge according to claim 1, in which said chamber has anoverflow outlet of limited outlet area and located radially between therotor axis and the outer part of said chamber.

8. A centrifuge according to claim 7, in which said overflow outlet isadjustable radially.

